Molten metal plating furnace, system for producing and method for producing plated product, and metal plated steel tube obtained by means of said method for producing

Abstract

[Problem] To provide: a molten metal plating furnace that can increase plating quality and work efficiency; a system for producing and method for producing a metal plated product; and a metal plated steel tube obtained by means of the method for producing. [Solution] The system for producing has at least one plating implementation unit that performs molten metal plating of a plating processing subject, and at least one plating implementation unit has a plating bath and a heating device for heating the plating bath, wherein in the heating device, an array of fuel filling openings and an array of air filling openings are formed that are facing in a manner so as to discharge air and fuel to a combustion region in common along a combustion chamber, the effective opening cross-sectional size of at least the majority of the openings of at least one of the opening arrays can be adjusted by means of an adjustment mechanism for adjusting the extent of a medium filling opening array, and when the size of both opening arrays can be adjusted, individual adjustment of the arrays is possible.

What is claimed is: 
     
       1. A molten metal plating furnace comprising:
 a plating bath; 
 an inner wall in a substantially rectangular shape disposed outside of the plating bath and made of side wall portions and end wall portions shorter than the side wall portions; 
 a heat-resistant outer wall in a substantially rectangular shape made of side wall portions and end wall portions shorter than the side wall portions; 
 the side and end wall portions of the inner wall facing the side and end wall portions, respectively, of the heat-resistant outer wall, thereby forming an annular heating chamber surrounding the plating bath; 
 and a heating device, the heating device being disposed on one end wall portion of the heat-resistant outer wall and configured to completely combust fuel within the heating device and situated so as to inject combustion gas molecules generated by the combustion in the heating device into the heating chamber at a site laterally offset from the end wall portion of the inner wall facing the end wall portion of the outer wall on which the heating device is disposed, to circulate inside the heating chamber; and 
 an exhaust port configured to exhaust part of the combustion gas molecules circulating inside the heating chamber, the exhaust port being disposed on the end wall portion of the outer wall on which the heating device is disposed, the exhaust port being situated so as to exhaust combustion gas molecules from the heating chamber at a site directly facing the end wall portion of the inner wall and laterally offset from the site at which combustion gas molecules are injected into the heating chamber by the heating device, 
 wherein the heating device is a combustor including a combustion chamber having a wall extending about a center axis, at least part of the axially extending wall is formed with an array of fuel charging orifices and an array of air charging orifices facing a common combustion zone along the combustion chamber to discharge fuel and air into the common combustion zone, sizes of the fuel charging orifices relative to those of the air charging orifices being predetermined to achieve an effective combustion reaction to produce the combustion gas molecules to be injected into the heating chamber, a progressively constricted combusted medium discharge nozzle is provided for accelerating the discharge velocity of the combustion gas molecules, and fuel and air supply chambers opening respectively into the fuel charging orifice array and the air charging orifice array are provided, an igniter configured to ignite a combustible mixture in the combustion chamber is provided; the combustor includes an adjustment device configured to adjust an effective cross sectional orifice size of at least a majority of orifices of at least one of the orifice arrays, and the adjustment device is configured to independently adjust the fuel charging orifice arrays and the air charging orifice arrays to adjust the respective flow of fuel and air. 
 
     
     
       2. The molten metal plating furnace claimed in  claim 1 , wherein the individual orifices of the arrays of the heating device are positioned and aimed to result in center axes of at least the majority of air charging orifices crossing center axes of corresponding fuel charging orifices along a longitudinal center of the combustion chamber that corresponds to the center axis of the combustion chamber. 
     
     
       3. The molten metal plating furnace claimed in  claim 1 , wherein the fuel charging orifice array and the air charging orifice array of the heating device have equal numbers of orifices. 
     
     
       4. The molten metal plating furnace claimed in  claim 1 , wherein the orifices of the fuel charging orifice array and of the air charging orifice array of the heating device are regularly spaced. 
     
     
       5. The molten metal plating furnace claimed in  claim 1 , wherein the orifices of the fuel charging orifice array and of the air charging orifice array of the heating device are spaced in rows and columns. 
     
     
       6. The molten metal plating furnace claimed in  claim 2 , wherein the center axes of all the orifices of the heating device are slanted at a same angle relative to the longitudinal center of the combustion chamber in a discharge direction of the heating device. 
     
     
       7. A method for producing a molten metal plated product using the molten metal plating furnace claimed in any one of  claims 1  to  6 , wherein the plating bath contains the molten metal, the method comprising heating the plating bath with the heating device and dipping a product into the plating bath thereby to plate the product and form the molten metal plated product. 
     
     
       8. The method for producing the molten metal plated product claimed in  claim 7 , wherein variation in temperature in the plating bath of the molten metal plating furnace is not greater than 20 degrees. 
     
     
       9. A system for producing a metal-plated product comprising at least one plating performing part that performs molten metal plating on an object to be plated, wherein
 at least one of the plating performing part includes a plating bath, an inner wall in a substantially rectangular shape disposed outside of the plating bath and made of side wall portions and end wall portions shorter than the side wall portions, a heat-resistant outer wall in a substantially rectangular shape made of side wall portions and end wall portions shorter than the side wall portions, the side and end wall portions of the inner wall facing the side and end wall portions, respectively, of the heat-resistant outer wall, thereby forming an annular heating chamber surrounding the plating bath, a heating device, the heating device being disposed on one end wall portion of the heat-resistant outer wall and configured to completely combust fuel within the heating device and situated so as to inject combustion gas molecules generated by the combustion in the heating device into the heating chamber at a site laterally offset from the end wall portion of the inner wall facing the end wall portion of the outer wall on which the heating device is disposed, to circulate inside the heating chamber; and 
 an exhaust port configured to exhaust part of the combustion gas molecules circulating inside the heating chamber, the exhaust port being disposed on the end wall portion of the outer wall on which the heating device is disposed, the exhaust port being situated so as to exhaust combustion gas molecules from the heating chamber at a site directly facing the end wall portion of the inner wall and laterally offset from the site at which combustion gas molecules are injected into the heating chamber by the heating device, 
 wherein the heating device is a combustor including a combustion chamber having a wall extending about a center axis of which at least part of the axially extending wall is formed with an array of fuel charging orifices and an array of air charging orifices facing a common combustion zone along the combustion chamber to discharge fuel and air into the common combustion zone with sizes of the fuel charging orifices relative to those of the air charging orifices being predetermined to achieve an effective combustion reaction to produce the combustion gas molecules to be injected into the heating chamber, a progressively constricted combusted medium discharge nozzle for accelerating discharge velocity of combustion gas molecules is provided, and fuel and air supply chambers opening respectively into the fuel charging orifice array and the air charging orifice array are provided, each array being connectable to a supply of fuel or air respectively, an igniter configured to ignite a combustible mixture in the combustion chamber is provided; wherein the combustor includes an adjustment device configured to adjust an effective cross sectional orifice size of at least a majority of orifices of at least one of the orifice arrays, and wherein the adjustment device is configured to independently adjust the fuel charging orifice arrays and the air charging orifice arrays to adjust the flow of fuel and air, respectively. 
 
     
     
       10. The system claimed in  claim 9 , wherein the individual orifices of the arrays of the heating device are positioned and aimed to result in center axes of at least the majority of air charging orifices crossing center axes of corresponding fuel charging orifices along the longitudinal center of the combustion chamber that corresponds with the center axis of the combustion chamber. 
     
     
       11. The system claimed in  claim 9 , wherein each of the orifice arrays of the heating device each has an equal number of orifices. 
     
     
       12. The system claimed in  claim 9 , wherein the orifices of each of the arrays of the heating device are regularly spaced. 
     
     
       13. The system claimed in  claim 9 , wherein the orifices of each of the arrays of the heating device are spaced in rows and columns. 
     
     
       14. The system claimed in  claim 10 , wherein all the center axes of the orifices of the heating device are slanted at the same angle relative to the longitudinal center of the combustion chamber in the discharge direction of the heating device. 
     
     
       15. The system claimed in any one of  claims 9  to  14 , wherein the metal-plated product is a metal-plated steel pipe. 
     
     
       16. The system claimed in any one of  claims 9  to  14 , wherein the system for producing the metal-plated product is a steel pipe producing system that produces a steel pipe plated with molten metal on inner and outer surfaces or one of the surfaces on a continuous production line from band steel, the system comprising: an inner surface plating performing part that performs the molten metal plating by pouring molten metal onto an upper side of the band steel of a side corresponding to an inner surface of the steel pipe; a steel pipe forming part to obtain a continuous steel pipe by continuously cold-forming the band steel in a tubular shape having the inner surface plated and seamlessly welding longitudinal-direction end face junctions of the band steel formed as the steel pipes; and an outer surface plating performing part that performs the molten metal plating by dipping an outer surface of the steel pipe into the molten metal, wherein the inner surface plating performing part and/or the outer surface plating performing part includes the plating bath and the heating device to heat the plating bath. 
     
     
       17. A method for producing a metal-plated object using the system claimed in any one of  claims 9  to  14 , wherein the plating bath contains the molten metal, the method comprising heating the plating bath with the heating device and dipping the object to be plated into the plating bath thereby to plate the object and form the metal-plated object. 
     
     
       18. The method for producing the metal-plated object claimed in  claim 17 , wherein the variation in temperature in the plating bath of the at least one plating performing part is not greater than 20 degrees. 
     
     
       19. The metal-plated object obtained by the method claimed in  claim 17 , wherein a thickness of a plated layer on the metal-plated object is 4 μm or less.